It had been an idyllic day celebrating a cousin's wedding until Steve's wife turned to him during the reception and said she was having a panic attack. The loud music in the room seemed to be engulfing her, heightening her anxiety. After the main course was served, Steve and his wife got up to go for a drive and get some air. To respect his wife's privacy, Steve did not tell anyone why they were leaving, including his half-sister, Klara, who was seated at their table.

Minutes after the two left the wedding, as Steve later learned, Klara started approaching family members to claim that Steve and his wife had stormed off over something she did—and that they'd refused to tell her what she'd done wrong. She marched from table to table sharing the story, adding more drama with each telling. She ended up in the ladies' room a few minutes later, sobbing, and it took Steve's mother, other sister, and several close friends to calm her down so she wouldn't disturb the festivities.

While trying to help his wife through her panic attack, Steve had stopped paying attention to his cell phone. When he next looked at the screen, he faced a torrent of messages from Klara, each more indignant than the last. "I deserve better... what the **** is wrong with you!... I HATE YOU!... Never call me again. You're dead to me!" Steve still marvels at how quick Klara was to erupt in response to her perception of events. "Despite there being no argument, no unpleasant words exchanged," he says, "our absence was presumed to be a slight directed at her and her alone."

Klara's spontaneous emotional combustion at the wedding would probably seem totally unremarkable to the 14 million adults in the U.S. who are estimated to have borderline personality disorder (BPD). They make up 2 percent of the general population but 20 percent of psychiatric inpatients. Most are women, and they typically turn the ups and downs of everyday life into a roller-coaster ride of moods. In doing so, they don't just alienate others around them, they subvert their own life trajectory. Explosively reactive, and often struggling to get a grip on themselves, borderlines have difficulty maintaining stable relationships or even holding down a job.

Borderlines are interpersonal tornadoes. Some men are even romantically drawn—at least for a while—to the drama such women create around them and the helplessness they often display. For decades, however, it has been an open secret that psychiatrists dislike dealing with borderline patients. In large part, their reluctance has been fueled by their own frustrations: There was little help to offer. And borderlines often become hostile to their helpers. But the availability of dialectical behavior therapy, an emerging understanding of the roots of the disorder, and a disentangling of the behaviors that characterize it have all begun to brighten the outlook for borderline patients.

Courting Chaos

The term borderline personality is highly evocative, suggesting someone living life on the edge. In reality, borderline personalities are characterized more by volatility than by risk. Emotional dysregulation and impulsivity are at the disorder's core. Sufferers swing from happiness to despair to fury, often in minutes, and each feeling is vastly disproportionate to its trigger. "Life is like a ship in a stormy sea without a keel," says New York psychiatrist Frank Yeomans.

If interacting with a borderline is confounding, the condition is highly disruptive to borderlines themselves. During her worst flare-ups, says Debbie Corso, a San Francisco author who also blogs about her disorder, her emotions became so overwhelming they gave rise to physical symptoms. "My head would feel like it was spinning. My breathing would become shallow and my muscles tense. I would get what I describe as a flush of cold adrenaline flooding through my body. The urge was to curl up in the fetal position and cry until I was so exhausted that I wanted to sleep."

Although BPD has long been ascribed to problematic parenting, scientists now believe that the borderline personality develops out of a neurobiological flaw. Borderlines exhibit a highly reactive limbic system in conjunction with a decreased capacity for cortical control of it, reports Mayo Clinic psychiatrist Brian Palmer. Vulnerability to the disorder appears to be inherited in the form of a tempestuous temperament, although early caretaking in some way seems to activate it.

The condition may not manifest until adolescence—often with self-cutting, burning, or frank suicidal behavior—but it begins long before. "As children, they are hard to parent," says Palmer. In the absence of exceptional parenting, they never achieve self-regulation or a stable sense of self and never learn to tolerate any distress.

"There's an inner sense of emptiness that can be haunting," observes Yeomans. Uncertainty about who they are often keeps them from following a clear path in life. "One day I'll be wearing Lilly Pulitzer and pearls and playing the role of a perfect Southern belle; the next I'll be dyeing my hair black, wearing tie-dye and hemp necklaces, smoking pot and listening to The Grateful Dead," writes borderline sufferer Jennifer O'Brien. "I've been to three different universities since I started college, and I've changed my major 10 times."

Seeding the emotional storms, says Harvard psychiatrist John Gunderson, director of the Borderline Personality Disorder Center at McLean Hospital, is a hypersensitivity to rejection. Borderlines are quick to assume others are excluding them—and quick to react to that perceived rejection. "Say you're having dinner with a borderline person and someone else comes into the room, and you start a conversation with that other person," Gunderson offers. "The borderline is liable to think that the other person is preferred, and to feel betrayed. When the other person leaves, the borderline will say something like, 'What was so good about her?'" Paranoia, especially arising in interpersonal conflict, has been one of the diagnostic criteria for borderline disorder.

Borderlines' all-consuming fear of rejection stems from a bone-deep terror that the people they're close to will abandon them. "My significant other travels to visit his family and conduct business overseas," Debbie Corso says. "Each time he traveled, I would become a complete and total mess—ending up in the emergency room dehydrated and having not eaten."

The fear of abandonment commonly drives borderlines to seek confirmation that they truly matter. In practice, it could mean interrupting a boyfriend during an important work meeting or showing up at his doorstep in pajamas in the middle of the night. "I feel I'm going to die if I can't contact the person," says "Kim," a 32-year-old mother from the Northeast who was diagnosed as borderline several years ago. "I don't care what the consequences might be of my contacting them. I know it isn't going to end well but I can't stop."

Their overwrought rejection sensitivity leads borderlines to assess other people and situations in all-or-nothing terms. "There's a tendency to operate in extremes—black or white, right or wrong," says psychiatrist Jerold Kreisman, author of I Hate You—Don't Leave Me: Understanding the Borderline Personality. "What they're feeling right now defines things: I have this friend I've known for 10 years, but we had this violent disagreement about politics and now I hate his guts.'" In a romantic context, a borderline person might tell her partner, "You're the most amazing guy I've ever met. I want to share my life with you," and a few hours later gather all his belongings and pile them in the driveway after he "rejects" her by talking to an ex for a few minutes at a party.

Chaos and crises, in fact, bring comfort to borderlines. "They actually feel safer in chaotic environments and relationships," says San Diego psychiatrist David Reiss. "In a chaotic situation, the person knows the territory. In a calm situation, the person feels insecure, not knowing when the next shoe will drop and unprepared for what type of abuse or disruption may lie ahead."

Chaos serves another important function for borderlines. It distracts them from their emotional turmoil, observes the Mayo Clinic's Palmer. Some of the signature behaviors of borderline personality disorder—self-cutting, sexual promiscuity, drug use, bingeing and purging, suicidal gestures—are attempts to escape from the intense negative emotions that overwhelm them. As a result, they often court chaos.

Intense Irony

The affirmation that borderlines pursue so desperately from others turns out to be the Achilles' heel of their lives. Their interpersonal intensity—emotional outbursts, heated middle-of-the-night exchanges—often jeopardizes their most important relationships. Calling a friend at four in the morning after a fight, pleading "I have to see you right now. I have to know that things are OK between us," is seldom endearing. Says Gunderson: "Borderlines engineer the ending of the very relationships they covet" by wearing out friends and loved ones.

And their behavior is so predictably unpredictable that it can be captured empirically. In a recent study, healthy subjects were partnered with borderline patients in an online game of strategy that required players to cooperate in order to succeed. But the borderline patients so frequently acted erratically and broke alliances that the healthy players stopped collaborating—even though it meant sacrificing potential "earnings."

"People with borderline personality disorder are characterized by their unstable relationships, and when they play this game, they tend to break cooperation," says Read Montague, director of the Human Neuroimaging Laboratory at Virginia Tech, who reported the findings in PLoS Computational Biology.

The chaos of everyday life can turn mundane events like completing a work project or submitting a tax return into Sisyphean tasks. "I've had a hard time keeping a job my entire life," reports Corso, who has worked as a preschool teacher, advertising assistant, telephone operator, makeup artist, and cashier, among other things. "When a crisis hit, I'd make a dramatic exit—never realizing that I could slow down, call in sick, and pull myself together. So my career path has been quite a struggle."

Fifty-Five Percent

"Less than schizophrenia but ahead of lots of other psychiatric disorders," says Palmer about the role genes play in the genesis of borderline personality disorder. "The condition is now believed to be 55 percent heritable." Increasingly, the origins of the condition are seen as a classic interplay of nature and nurture.

The parental role is complex, says Gunderson. Children who develop BPD inherit a temperament—one that makes them highly reactive, emotional, and so hypersensitive to perceived anger or rejection they might cry inconsolably if scolded—that can tax even a good caretaker. "The hostile, conflicted relationships that evolve are not, as traditionally thought, a result of poor parents, but of parents whose parenting is shaped by a difficult child. It might take an extraordinarily calm parent to keep a genetically loaded infant from developing the disorder."

Researchers have identified unusually heightened activity in the amygdala, a brain structure that forms part of the limbic system, which governs memory and the sense of smell as well as emotional reactivity. They believe the reactivity gives rise to a hair-trigger temper. In addition, many borderline patients have a specific short variant of the serotonin transporter, or 5-HTT, gene. It affects how much neurotransmitter is available to nerve cells, and the short allele has been linked to anxious, aggressive, and impulsive behavior.

But abusive parenting and other traumaticchildhood experiences still seem to figure into the disorder. A large number of sufferers do, in fact, have incidents of physical or emotional abuse in their past, although in some cases they may be the result of a difficult-to-manage temperament, not its cause.

Psychiatrist Otto Kernberg of New York's Weill Cornell Medical College, one of the first researchers to describe the borderline personality, has long seen an overly rigid approach to life as a consistent feature. In his view, it evolves out of direct experience of physical or emotional abuse or witnessing others being abused, though he acknowledges the contribution of such biological defects as an overactive amygdala. He finds that borderline patients have a tendency to separate experiences into "positive" and "negative" buckets in their mind—a maneuver they engage in, he says, to prevent positive experiences from being contaminated by negative ones. A person may cling to sunny memories of his mother buying him an ice cream cone, for example, even though she abandoned him later on.

As they mature, borderlines continue to idealize some things and demonize others to make sense of a world that seems frightening. "There's a lack of capacity for a realistic assessment," says Kernberg. A friend who merited endless love on Monday could be persona non grata by Tuesday because she turned down an invitation to coffee.

Perhaps as part of an attempt to cope with abuse, borderline patients may have a distorted perception of time, says San Diego's David Reiss. They see it more as an accumulation of distinct events than a continuous linear progression. It leads to difficulty in perceiving the chronological sequence of events. The misperception of time may compound the problems borderlines face in fulfilling life responsibilities.

Intractable No More

Perhaps the most remarkable aspect of borderline personality disorder is the view that has emerged over the past decade that, despite the array and depth of deficits, it is not an intractable condition. With treatment, symptoms like suicide attempts and cutting remit. "Most patients lose some symptoms rapidly," observes McGill University psychiatrist Joel Paris.

The most specific and best-evaluated treatment for borderline personality disorder is dialectical behavior therapy. Developed by University of Washington psychologist Marsha Linehan, DBT grew out of her failed attempts to treat borderlines with traditional cognitive behavior therapy. Patients perceived its emphasis on change as totally invalidating and often dropped out of therapy. The "dialectical" in DBT reflects the paradox at its heart—communicating radical acceptance in the face of constant self-invalidation while recognizing the need for change.

The therapy aims first to diminish suicidal behavior, then to impart such basic behavioral skills as emotion regulation and distress tolerance. "The ultimate goal of treatment," Linehan has said, is "to move the client from a life in hell to one worth living, as quickly and efficiently as possible."

Since the early 1990s, randomized trials have shown that, compared to treatment as usual, DBT diminishes attempts at suicide and self-harm and reduces psychiatric hospitalizations. Even a year after the end of treatment, patients also report less anger and depression.

If there is a problem with DBT, it is that it is not widely available. What's more, it is costly and lengthy, says Paris. Only a small percentage of patients wind up getting DBT. "It needs to go from elite to accessible," he says. Further, he questions whether it needs to last for a year. "There's evidence that most of the changes occur in the first six months. Nevertheless, we've all been influenced by it. We've all become much more practical about treatment," focusing on imparting behavioral and life skills.

Another psychotherapy specifically developed to treat borderline patients, mentalization therapy, draws more on psychodynamic principles. In both group and individual sessions, patients learn to recognize the emotional states of themselves and others and how they give rise to specific behaviors.

Still, holding a job is an achievement for borderlines. Recent studies show that even after symptoms like self-injury remit with therapy, as few as a third of sufferers are able to work full-time. Many hold part-time jobs or positions that are not self-supporting. "Once they are off their life trajectory," observes the Mayo Clinic's Palmer, "getting on a path is difficult."

The real problem with treating borderline personality disorder, however, is that patients don't get the right diagnosis. Many are misdiagnosed as having bipolar disorder and treated accordingly. "Lots of patients are on antipsychotics, mood stabilizers, and antidepressants," says Paris. "They may be taking four or five drugs. They are not getting psychotherapy, and many insist on staying on pills. Borderline personality disorder is a condition in which psychotherapy is more effective than drugs. The evidence for drugs in the treatment of BPD is very weak."

Debbie Corso says she "found the way out of hell" with DBT. "My journey proves that people can and do get better from this condition. There is definitely hope." She is thrilled that she no longer meets the criteria for diagnosis—that she has moved, she says, "beyond the borderline."